He also reveals the Thriller singer’s reliance on painkillers — “kick-started by Klein” — got so bad that he and Geller considered KIDNAPPING him “to get him off the drugs”.

Former child star Mark is godfather to Jacko’s three children and has always suspected he could be the biological father of Prince’s younger sister, Paris. He is willing to take a DNA test when she turns 18 next April “if she wants me to”.

“Marlon obviously would have been in his mid-sixties or even slightly older but these things still happen.

“There’s also the possibility that something could’ve been put on ice.”

Mark met Brando at Jackson’s Neverland ranch shortly before the actor’s death and recalls: “He spent many of his dying days there.

“He wasn’t the only one who would be invited. Leonardo DiCaprio would often stay. On another occasion I saw Venus and Serena Williams using one of his tennis courts. It was remarkable.

“I went round to say hello to Brando. He was sat with his eyes closed with Michael and as I got in close he suddenly opened his eyes. It scared the life out of me. He looked remarkably like Prince does now.”

While his admiration for Brando is clear, Mark struggles to hide his disdain for Klein, who died in hospital last month, aged 70, after being admitted with abdominal pains.

The doctor’s star-studded patient list included Cher, Dolly Parton and Sharon Stone. He also employed Jackson’s future wife — and Prince and Paris’s mum — Debbie Rowe, now 56, as his assistant.

Mark, who played the title role in 1968 film Oliver!, claims multiple sclerosis sufferer Klein made sure his own sperm sample was at the front of the queue. He says: “Klein was no good for Michael. He was out for his own gain.

“It would not surprise me if he inseminated his own sperm into Debbie.

“Klein would’ve been in control of the whole thing and his link to Debbie makes him the most likely candidate to be Prince’s father.

Mystery has surrounded the biological fathers of Prince and Paris since Jackson’s sudden death, aged 50, in 2009. It has been claimed Jackson, fearing he would pass on his vitiligo skin condition, chose donors who he believed would make “genetically perfect” children.

There was also speculation past drug abuse had left him infertile.

Hours before Klein’s death, Prince reignited rumours in a Twitter post. Replying to a tweet that he was not a Jackson, Prince wrote: “The blood of the covenant is thicker than the water of the womb.

“I was raised by my dad with my brother and sister.”

The exchange prompted Mark to speak out. The dad-of-four says: “Michael was not really interested in the act of sex but rather wanted one of his inner circle to help him.

“He came to me on the phone one day in the Nineties and said I was clearly doing something right as I’d had four children. I thought it was a joke, then realised he was serious.

“I helped him but I have heard there was around half a dozen of his close circle.

“He was very close with Macaulay and I would be surprised if he wasn’t asked, despite him being 16 or so.

“For Michael it was all about aesthetics — he wanted the right genes for his kids.”

It was rumoured he used around 51 ultra-strong injections in three months.

Mark believes Michael’s operations, which included skin grafts and treatments of the sedative Propofol, cost the singer “in excess of £10million”.

He adds: “I believe Klein got Michael hooked on surgery so that he always wanted the next step, which would always be at great expense.

“I remember meeting him at a hotel in London and it was clear he had control of Michael.”

Mark also blamed Klein for Jackson becoming addicted to painkillers for a decade before his death.

He says: “I have no doubt this reliance on strong drugs to numb the pain was kick-started by Klein and carried on by Dr Murray, his go-to man at the end. At one point Uri Geller and myself even considered kidnapping him to intervene and get him off the drugs.”

In 2009, three months after announcing his London O2 shows, Jackson, who was said to be £100million in debt, was found dead after overdosing on painkillers and tranquillisers.

Murray, now 62, was convicted of the star’s manslaughter and jailed for four years.

Klein filed for bankruptcy in 2012 after reportedly spending more than £4million on luxuries.

Mark, who runs an osteopath business in Cheltenham, Gloucs, says: “I have no doubt Michael would still be here today if it wasn’t for what Klein and the others did to him.